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The Planets this Month - April 2013

Mercury

During April, Mercury remains well placed for observation before dawn for observers located in the tropics and at southern hemisphere latitudes. For those at northern temperate latitudes, the angle of the ecliptic is unfavourable and the planet is not visible this month.

On March 31st, the closest planet to the Sun reached greatest elongation west (28 degrees from the Sun). On this date, from latitudes of 35S (approx. equal to Sydney, Cape Town and Santiago) it was positioned 20 degrees above the eastern horizon, 30 minutes before sunrise.

The planets altitude will slightly decrease each subsequent morning as the month progresses but at the same time it increases in brightness. Mercury starts April at magnitude 0.3 and finishes the month at magnitude -1.0.

On April 8th, the thin waning crescent Moon will pass 7 degrees north of Mercury and on April 19th, Mercury will be positioned 2 degrees south of Uranus (mag. 5.9).

The diagram below shows the March and April morning apparition of Mercury from latitude of 35S.

Venus

Venus passed through superior conjunction on March 28th. The planet is now located on the far side of the Sun and consequently unsuitably placed for observation throughout April.

Mars

Mars reaches solar conjunction on April 18th and therefore is positioned too close to the Sun to be observed this month.

Jupiter

Jupiter remains an evening object throughout April. The largest planet of the solar system is visible in the southwest sky as soon as it gets dark, but now sets before midnight by months end from northern temperate latitudes. The period of visibility is even less for those located further south.

The giant planet continues it direct motion in Taurus. At the start of April it's positioned only 5.5 degrees north of magnitude 0.9 orange/red star Aldebaran and the famous "V" shaped Hyades open cluster. By the end of the month Jupiter has moved to 9 degrees northeast of Aldebaran and continues to gradually drift away from this prime section of zodiac "real estate".

The planets magnitude decreases from -2.1 to -2.0 during April with the apparent size diminishing from 36 to 34 arc seconds over the same time period. On April 14th, the waxing crescent Moon passes 2 degrees south of Jupiter between the "horns" of Taurus, the Bull.

Saturn reaches opposition on April 28th (mag. 0.1) and on this date is located 8.816 AU (approx. 1319 million km or 819.5 million miles) from Earth. It rises towards the east-southeast and is visible as soon as it gets darks and remains so all-night. The far away planet with its beautiful set of rings, is currently moving retrograde amongst the faint stars of western Libra.

During April, the brightness of Saturn increases slightly from magnitude 0.3 to 0.1, with an apparent diameter of 19 arc seconds.

From our perspective, Saturn's rings are titled at approx. 19 degrees and are a wonderful sight through telescopes. They are visible in even the smallest of instruments and are a must see on all astronomers observation lists. Larger telescopes reveal subtle details, with many of the planets brightest moons visible.

In Pisces, for northern hemisphere observers not suitably placed for observation during April, but visible as a very early morning object during the second half of the month for those located further south.

Uranus shines at magnitude 5.9 and on April 19th, Mercury (magnitude -0.3) passes 2 degrees south of the very distant green planet, just before sunrise.

Neptune

Neptune, magnitude 8.0, is currently located in Aquarius. It remains unsuitably placed for observation throughout April from the northern hemisphere but can be seen in the early morning sky from tropical and southern latitudes.